Light is the Genesis-creation of the world: the primary utterance of creation is "Let there be light," and the first act of creation is the distillation of light, its separation from darkness.
The Midrash asks: Where was light created from?
And the answer is whispered: "God cloaked Himself in a white shawl, and the light of its splendor shone from one end of the world to the other" (Genesis Rabbah 3:4).
In other words, light, fundamentally, does not belong to this world.
It is, rather, an emanation of a different essence, from the other side of reality.
Light serves as the symbol of the good and the beautiful, of all that is positive.
The difference between light and darkness assumes such a general and metaphysical significance, and the advantage of light over darkness is so obvious and self-evident, that it serves as a sharp metaphor: "Wisdom excels folly as far as light excels darkness" (Ecclesiastes 2:13).
Light as a positive symbol is so prevalent in biblical Hebrew that redemption, truth, justice, peace, and even life itself "shine," and their revelation is expressed in terms of the revelation of light.
The symbolism of light goes even higher than that: Divine revelation itself is a revelation of light, the tzadikim in the Garden of Eden "bask in the light of Shekhinah," and even God Himself is "my light and my salvation" (Psalm 27:1).
Hence, too, in the language used by the kabbalists, all of reality is "lights" and "enlightenments," all the way up to "the light of the Infinite, be blessed."
–Rabbi Adin Steinsaltz
In On Being Free, p. 181, by Rabbi Adin Steinsaltz